Gregory ordained Dominic a priest. Together they built a wooden bridge over the Oja River to help pilgrims on the Way of St. James. Gregory died in 1044, and Dominic returned to Ayuela, where he began developing the area. He cleared trees, cultivated the earth, and began to build a paved causeway (in Spanish, calzada), which served as an alternate route to the traditional Roman causeway between Logroño and Burgos. Dominic's causeway became the principal route between Nájera and Redecilla del Camino.[2]

Dominic was joined in this work by Juan de Ortega. To better the conditions of the pilgrims that began to use his new causeway, he replaced the wooden bridge that he had built with Gregory with one made of stone, and constructed on the site of an old fort, a building that served as a hospice for travelers. Today, it is the Casa del Santo, which is a used as a hostel by modern-day pilgrims.[2]

The town of Santo Domingo de la Calzada began as a few houses built around the hermitage of the saint in his lifetime. At this death in 1109, the village had grown in population. Alfonso VI of Castile annexed La Rioja in 1076 and seeing that Dominic's efforts contributed to the Castilianization of the region, decided to support him and his projects. He visited Dominic in 1090 and thereafter Dominic, assisted by his follower Juan de Ortega, began construction on a church dedicated to Christ and the Virgin Mary. This was consecrated by the bishop of Calahorra in 1106.[2]

Miracles are attributed to Dominic, among them the healing of a Frenchknight who had been possessed by the devil and who was freed of his affliction by visiting the sepulcher of the saint. Another concerns the healing of a German pilgrim named Bernard in the fifteenth century, who was cured of an affliction of the eyes by visiting the saint's tomb. Another concerns the healing of a blind Norman who was cured when he visited the cathedral.[2]

The most famous miracle, however, concerns that of the rooster and the chicken, which is said to have taken place at Santo Domingo de la Calzada.[4] The story goes that in the 14th century, a German 18-year-old named Hugonell, from Xanten, goes on pilgrimage to Santiago de Compostela with his parents. A Spanish girl at the hostel where they were staying makes sexual advances toward Hugonell; Hugonell rejects her advances. Angry at this, the girl hides a silver cup in the German's bag and then informs the authorities that the youth had taken it. Hugonell is sentenced to the gallows, in accordance with the laws of Alfonso X of Castile.

The parents sadly decide to examine their son's body, still hanging on the gallows, but suddenly hear his voice –he tells them that Saint Dominic has saved his life. His parents quickly make their way to Santiago de Compostela to see the magistrate. The magistrate, who is at the time eating dinner, remarks: "Your son is as alive as this rooster and chicken that I was feasting on before you interrupted me." And in that moment, the two birds jump from the plate and begin to sing and crow happily.[4]

The second part of the tale, the miracle of the dancing roasted chicken and rooster, is unique to Santo Domingo de la Calzada,[5] although a very similar story appears in the English carol "King Herod and the Cock",[6] and related notions can also be found in folklore concerning the mythical land of Cockaigne, "where grilled geese fly directly into one's mouth".[7]

In memory of Dominic's miracle, a rooster and chicken, with white feathers, are kept alive at the cathedral all year round.[5] A different rooster and chicken are switched each month, although they are called descendants of the original birds who miraculously danced even though roasted. The pairs of roosters and chickens, when they are not at the cathedral, are kept in a chicken coop called the Gallinero de Santo Domingo de la Calzada, which the Cofradía de Santo Domingo (Confraternity of Santo Domingo) maintains with the help of donations. A wayside shrine (hornacina) built in 1445 holds a relic associated with the miracle: a piece of wood from the gallows from which Hugonell was hanged.

Medieval pilgrims gathered the feathers of these favored birds, or got them from the priest, and would affix them to their hats.[5] Another tradition claimed that if the birds ate breadcrumbs directly from the end of the pilgrim’s staff, that pilgrim would arrive safely in Compostela.[5]

The German pilgrim Hermann Künig (15th century) claimed to have seen the room where the roasted birds began to sing and dance; other documents written by pilgrims state that Hugonell’s shirt as well as the gallows had been conserved by the church of Santo Domingo. These artifacts are now lost.[5]